The Spurs’ night began with a bang, with Danny Green grabbing the opening tip and zooming for a left-handed dunk.

It ended with a 96-86 victory over Washington that extended the Spurs’ winning streak to a season-best 10 games as they prepare to head out on their annual rodeo road trip later this week.

What should have been a Saturday night to celebrate, or at least appreciate, became a night of uncertainty when All-Star forward Tim Duncan crumpled to the floor with 3:54 left in the first half after Wizards forward Martell Webster rolled up on the back of his legs.

“I don’t think I’ve ever seen Timmy like that before,” Green said. “I’ve seen him hurt before — banged and bumped and bruised — but usually he gets right back up.”

This time, Duncan had to be escorted off the floor with teammate DeJuan Blair under one arm and Stephen Jackson under the other. Television cameras later caught Duncan walking to the locker room on his own.

The initial diagnosis was a sprained left knee and sprained right ankle, but the full extent of the injuries likely will not be known until the 36-year-old is re-examined at some point later this week.

For now, Duncan’s teammates are finding hope in the fact that he exited the AT&T Center after the game under his own power, without crutches or any other assistance.

“I don’t know the ins and outs of what happened,” Jackson said, “but I saw him walk out of there, so that’s always good.”

Pessimists might recall that Boston’s Rajon Rondo recently played an entire fourth quarter on a knee that turned out to be season-endingly shredded.

Optimists might retort it is unlikely Spurs doctors would allow the team’s star to amble out of the arena under his own power if they feared the worst.

What is certain is this: The status of Duncan’s left knee just became the most important storyline of the Spurs’ season.

Before Saturday, the Spurs (38-11) won four consecutive games without Duncan, who sat out with a sore left knee. They held on against the 11-35 Wizards — despite squandering all but six points of a 27-point lead during a 30-9 Washington run in the second half — with Duncan in the locker room.

But the Spurs are going nowhere in May and June without him.

“Today, it looked like he was feeling good in layup lines, and he started out good, playing well in rhythm,” said Green, who had 15 points as the Spurs won their 18th straight at home. “To see him go down kind of sucks, not just for him but for us.”

Washington coach Randy Wittman said he heard Duncan’s injuries were not serious.

“I just talked to (the Spurs’) doctors, and they said he’s going to be fine,” Wittman said.

Spurs coach Gregg Popovich had no update to the initial injury report during a hurried postgame news conference. It appears likely the team will open the rodeo trip Wednesday in Minnesota without the player who is their second-leading scorer, leading rebounder and shot-blocker and foundational cornerstone.

The injuries came in Duncan’s first game since Jan. 21. The Spurs were in the process of seizing control of the game a 20-1 spurt near the end of the first half.

Driving toward the basket, Webster got stripped in mid-air by the Spurs’ Kawhi Leonard, then fell to the floor and rolled into the back of Duncan’s legs. The unexpected blow sent Duncan sprawling and clutching his left knee.

“I lost my footing, right there in the air,” Webster said. “That’s an unfortunate situation. I was sad to see him go down.”

Green finished a layup at the other end, then Popovich instructed point guard Tony Parker to foul the nearest Wizard to get Duncan off the floor. The sellout crowd of 18,581 fell silent.

“My prayers, my heart goes out to him that everything is OK, and he has a speedy and healthy recovery,” Webster said.

Parker, who led the Spurs with 19 points and 12 assists, said he was heartened after talking to Duncan postgame.

“He was pretty positive,” Parker said. “He’s fine. It’s nothing big.”

Whether that prognosis holds up — or turns out to be wishful thinking — remains to be seen. Spurs fans will have to wait until medical tests confirm Duncan’s diagnosis before they can properly exhale.